Fannie Mae and Freddie Mac are in talks with Obama administration officials to join fledgling government programs aimed at reducing loan balances of mortgages where borrowers owe more than their homes are worth, according to people familiar with the situation. An agreement with the two government-owned mortgage giants to write down so-called underwater loans could reduce the threat to the U.S. housing market from the glut of homeowners believed at risk of default should their personal finances or home prices worsen. A deal would deepen losses at Fannie Mae and Freddie Mac, which already have cost taxpayers about $134 billion.